Organic Chemistry- Alcohols Flashcards
What are the most common chemicals you’ll find in organic chemistry?
Alcohols
Alcohols have the general formula of what?
ROH
What functional group are alcohols in?
-OH referred to as a hydroxyl group
How are alcohols named in the IUPAC system?
Replacing the -e ending of the root alkane with the ending -ol
What happens if alcohol is the highest priority functional group when bonding?
The carbon atom attached to it receives the lowest possible number
What happens if alcohol is not the highest priority function group when bonding?
It is named as a substituent, with the prefix hydroxy-
What is the common naming practice for alcohols?
To name the alkyl group as a derivative followed by alcohol
Hydroxyl groups can be attached to what? What is it called?
Aromatic rings
Called phenols
The hydroxyl hydrogens of phenols are particularly, what? why?
Acidic due to resonance within the phenol ring.
What should you do if benzene rings contain 2 substituents?
Their relative positions must be indicated.
What must be added to the name, if two substituents are on adjacent carbons on a benzene ring?
Ortho- or simply O-
What must be added to the name, if two substituents are separated by a carbon on a benzene ring?
meta- or m-
What must be added to the name, if two substituents are on opposite sides of a benzene ring?
Para- or p-
What is one of the prominent properties of alcohols? Which results in what?
They are capable of intermolecular hydrogen bonding, which results in significantly higher melting and boiling points than those analogous hydrocarbons
What should you lookf for in an alcohol molecule to know if there is greater hydrogen bonding? What else can you look for?
Molecules with more hydroxyl groups show greater degrees of hydrogen bonding.
Boiling point increases significantly with additional hydroxyl groups which permit more hydrogen bonding.
When does hydrogen bonding occur?
Hydrogen bonding occurs when hydrogen atoms are attached to highly electronegative atoms like nitrogen, oxygen, or fluorine
Hydrogen bonding is the result of what?
The extreme polarity of these bonds.
In the case of a hydroxyl group, what happens during hydrogen bonding?
The electronegative oxygen atom pulls electron density away from the less electronegative hydrgen atom. This generates a slightly positive charge on the hydrogen and slightly negative charge on the oxygen. Then, the partially positive hydrogen of one molecule electrostatically attracts the partially negative oxygen of another molecule, genrating a noncovalent bonding force known as a hydrogen bond.
Hydroxyl hydrogens are weakly what?
Acidic
What can alcohol dissociate to?
Protons and alkoxide ions in the same way that water dissociates into protons and hydroxide ions
What are the dissociations of 7 hydroxyl-containing compounds?
H20 HO + H+ CH3OH CH3O + H+ C2H5OH C2H5O- + H+ I-PrOH i-PrO + H+ t-BuOH t-BuO- H+ CF3CH2OH CF3CH2O + H+ PhOH PhO- + H+
What are more acidic than other alcohols? Why?
Hydroxyl hydrogens of phenols. This is due to the armoatic nature of he ring which allows for the resonance stabilization of the negative charge on oxygen, stabilizing the anion.
Like other alcohols, What do phenols form?
Intermolecular hydrogen bonds and have relatively high melting and boiling points.
Phenol is slightly soluable in what? Why?
Water, owing to hydrogen bonding, as are some of its derivatives
Phenols can form what, that other alcohols can’t? Why?
Salts with inorganic bases such as NaOH
Because phenols are more acidic then other alcohols
The presence of other substituents on the ring has significant effect on what?
The acidity, boiling points, and melting points of phenols.
What increases and decreases acidity?
Electron-withdrawing substituents increase acidity
Electron-donating groups decrease
The presence of more alkyl groups in non aromatic alcohol produces what? Why?
Less acidic molecules because alkyl groups donate electron density, they destabilize a negative charge.
Alkyl groups help do what? Explaining why what happens?
Stabilize positive charges, explaining why more substitued carbocations have higher stability than less
What are the main reactions for alcohols seen on the MCAT?
Oxidation preparation of mesylates and tosylates, and protection of carbonyls by alcohols.
Primary alcohols can be oxidized to what? By what?
To aldehydes, but only by PCC.
What is pyridinion Chlorochromate?
A mild anhydrous oxidant
When does the oxidation of primary alcohols stop? Why?
After the primary alcohol has been converted to an aldehyde because PCC lacks the water necessary to hydrate the otherwise easily hydrated aldehyde
With other oxidizing agents added to the oxidation of primary alcohol, what happens?
Aldehydes are rapidly hydrated to form geminal diols, which can be easily oxidized to carboxylic acid.
Secondary alcohols can be oxidized by what? Into what
To ketones by PCC or any stronger oxidizing agent.
Tertiary alcohols can be oxidized to what?
They cannot be oxidized because they are already as oxidized as they can be without breaking a carbon-carbon bond.
What strong oxidizing agent can result in primary alcohols being oxidized to carboxylic acid? What is the process?
Chromium (VI)
In the process, chromium (VI) is reduced to chromium (III)
What are common examples of chromium-containing oxidizing agents?
Sodium and potassium dichromate salts (Na2Cr2O7 and K2Cr2O7)
Strong oxidizing agents will cause secondary alcohols to oxidize to what?
Ketones
What is Jones oxidation?
An even stronger chromium-containing oxidizing agent is chromium trioxide, CrO3, and it is dissolved with diulte sulfuric acid in acetone
What can jones oxidation oxidize primary and secondary alcohols to?
Carboxylic acids and ketones
Hydroxyl groups are fairly poor what?
Leaving groups for nucleophilic substitution reactions
What can be done to hydroxyl groups to make them better leaving groups?
Protonated, or reacted to form much better leaving groups
When a hydroxyl group is protonated or reacted to from better leaving groups what are they called?
Mesylates and tosylates.
What is a mesylate?
a compound containing the functional group -SO3CH3, derived from methanesulfonic acid.
How are mesylates prepared?
Using methylsulfonyl chloride and alcohol in the presence of a base.
What are tosylates?
They contain the functional group -SO3C6H4CH derived from toluenesulfonic acid.
How are tosylates produced?
By reaction of alcohols with p-toluenesulfonyl chloride, forming esters of toluenesulfonic acid.
What can mesyl and tosyl groups also do? Why?
Serve as protecing groups when we do not want alcohols to react. These groups are protective in that they will not react with many of the other reagents that would attack alcohols, especially oxidizing agents.
What should you do if your desired products do not derive from alcohols?
Reacting Mesyl or tosylate to the alcohols
Alcohols can be used themselves for what?
As protecting groups for other functional groups
How are acetals formed?
Aldehydes are reacted with two equivalents of an alcohol or a diol
What’s an acetal?
Primary carbons with two -OR groups and a hydrogen atom.
How are ketals formed?
Ketones are reacted with two equivalents of an alcohol or a diol
What is a ketal?
Secondary carbons with two -OR groups.
Carboxyls are very reactive with what?
Strong reducing agents like lithium aluminum hydride (LiAlH4)
What are not reactive with LiAlH4?
Acetals and ketals
What is the functionality of the acetal and ketal?
protects the aldehyde or ketone from reaction
What is deprotection?
After reducing other functionalities in the molecule, the acetal or ketal can be reverted back to a carbonyl with aqueous acid
How are quinones formed?
Treatment of phenols with oxidizing agents produce compounds called quinones (2,5-cyclohexadiene-1,4-diones)
How are quinones names?
by indicating the position of the carbonyls numerically and adding quinone to the name of the parent phenol.
Quinones are what? Due to What?
Resonance-stabilized electrophiles
Due to the conjugated ring system
are quinones aromatic? Why?
Not necessarily.
Because they lack the classic aromatic conjugated ring structure. Some quinones do have aromatic ring, but this is not always the case.
Wuinones serve as what?
electron acceptors biochemically, specifically in the electron transport chain in both photosynthesis and aerobic respiration.
Vitamin K1 is the common name of what?
Quinone 2-methyl-3-[(2E)-3, 7, 11, 15-tetramethylhexadec-2-en-1-yl]naphthoquinone
What is another name for vitamin K1?
Phylloquinone
Phylloquinone is important for what?
For photosynthesis and the carboxylation of some of the clotting factors in blood.
Vitamin K2 corresponds to what class of molecule?
Menaquinones
Menaquinones can be further oxidized to form what?
Hydroxyquinones.
Hydroxyquinones are similar and different how?
They share the same ring and carbonyl backbone as quinones, but differ by the addition of one or more hydroxyl groups.
Hydroxyquinones are used for what?
The synthesis of medications
Why do hydroxyquinones act like quinones?
Because resonance,
Hydroxyquinones are slightly less what compared to quinones?
electrophilic (but still reactive)
How are hydroxyquinones named?
The position of the hydroxyl group is indicated by a number, and the total number of hydroxyl groups (if there is more than one) is indicated by a prefix (such as di-, tri-) with the substituent name hydroxy-
What is a biologically active quinone?
Ubiquinone
What is another name for Ubiquinone?
Coenzyme Q
What is the vital job of Ubiquinone?
Vital electron carrier associated with complexes I, II, and II of the electron transport chain.
Ubiquinone is the most ________ form that his molecule takes physiologically.
Oxidized
What can Ubiquinone be reduced to?
Ubiquinol upon acceptance of electrons
What allows ubiquinone to perform its physiological function of electron transport?
This oxidation-reduction capacity
The long alkyl chain of Ubiquinone allows it to what?
To be lipid soluble, which allows it to act as an electron carrier within the phospholipid bilayer.
What are other biological molecules that undergo oxidation-reduction reactions as part of their normal function?
NADH,
FADH2
NADPH
NADH, FADH2, and NADPH do what?
accept and donate electrons readilty, similar to ubiquinone
